The Current State of Targeted Muscle Reinnervation: A Systematic Review

Abstract

Background Targeted muscle reinnervation (TMR) is growing in popularity; however, literature evaluating patient characteristics and outcomes is limited. Methods The EMBASE database was queried with the search terms “targeted muscle reinnervation” OR “TMR” AND “outcomes” OR “patient outcomes.” Clinical human studies in English were eligible for inclusion, yielding 89 articles. After rigorous exclusion criteria, a total of 13 articles were included in this review. Study data including geographic location, patient demographics, TMR indication, amputation level, number of nerve transfers performed, length of follow-up, and reported outcomes were extracted and analyzed. Results The included articles represent 338 patients (341 limbs). Average patient age was 47.4 years. Indication for amputation included trauma (n = 125), infection (n = 76) cancer/tumor resection (n = 71), ischemia (n = 18), failed Charcot reconstruction (n = 15), failed hardware (n = 9), burn (n = 4), and CRPS (n = 4). Five studies included upper extremity TMR only, two included lower extremity TMR only, and six included both upper and lower extremity TMR. TMR was performed in an immediate or delayed fashion, with an average of 2.2 nerve transfers performed per limb overall. Average length of follow-up was 22.3 months. In three studies, patients with phantom limb pain undergoing delayed TMR were found to have significant or trending toward significant reduction in pain after TMR using numeric rating scale and patient-reported outcomes measurement information system scales. One article reported 9/10 patients with improved or complete resolution of phantom limb pain after delayed TMR. Three studies found that patients undergoing immediate TMR had lower pain scores compared with non-TMR controls. Conclusion While there is evidence that TMR reduces neuroma-related pain and improves the quality of life for amputees, further outcomes studies are needed to study the patient experience with TMR on a larger scale. Establishing standardized, validated patient-reported outcomes assessment tools is critical to future investigation in this field.

The application of targeted muscle reinnervation in lower extremity amputations: A systematic review

“…Only one study incorporated validated functional assessment tools such as Orthotics Prosthetics User Survey (OPUS) and Neuro‐Quality of Life (Neuro‐QOL), which were reported as secondary outcomes (Mioton et al, 2020). A recent systematic review highlighted the need for standardized patient‐reported tools to understand long‐term patient experience following TMR (Walsh et al, 2023). Given the inextricable tie between LE amputation and function, this need is amplified in the LE TMR population.…”

“…Two recent systematic reviews corroborate these findings through aggregate assessments of postoperative outcomes (McNamara & Iorio, 2020;Walsh et al, 2023). However, both reviews combine postoperative outcomes across UE and LE amputation populations, making it difficult to provide detailed analysis of intraoperative technique outcomes, and complications specific to the LE.…”

Primary Targeted Muscle Reinnervation in Above-Knee Amputations in Patients with Unsalvageable Limbs from Limb-Threatening Ischemia or Infection

“…TMR has now been demonstrated by multiple groups to treat RLP and PLP secondarily and to help prevent development of such pain when performed primarily at time of amputation. [32][33][34][35][36][37][38][39][40][41][42]47 This article is protected by copyright. All rights reserved.…”

“…TMR has now been demonstrated by multiple groups to treat RLP and PLP secondarily and to help prevent development of such pain when performed primarily at time of amputation. 1,2,[31][32][33][34][35][36][37][38][39]42 Our institution recently reported outcomes on 100 patients receiving primary TMR at time of below-the-knee amputation (BKA). 43 Our study found that, relative to 100 patients undergoing a BKA with traction neurectomy of all identified nerves, patients receiving TMR experienced significantly lower rates of overall pain, RLP, and PLP; decreased usage of narcotics; and increased ambulation.…”

Targeted Muscle Reinnervation in the Setting of Traumatic Bilateral Above-Knee Amputations

“…The novel concept of targeted muscle reinnervation (TMR) was first described in the early twenty-first century after a bilateral shoulder disarticulation amputee underwent brachial plexus nerve transfers to the pectoralis major and minor, demonstrating enhanced prosthesis control on electromyogram 11,12 . TMR uses the principles of reinnervation, by taking free nerve endings and coapting them into motor branches of deinnervated muscles, to prevent neuroma formation 1,13-16 . In other words, TMR “gives a free nerve somewhere to go and something to do.” TMR has been shown to reduce neuroma formation and chronic phantom limb pain and increase ambulatory rates, even in highly comorbid patients.…”